Start this party about level 2 or 3, as commoners.
In the dusty magic poor kingdom of A'lenar tel A'ner (Aner for short) a Pixie escapes from bondage, fleeing to the kindest looking people she can find, she promises the PCs she will teach them the secrets of arcane power if they can A) Retrieve her tiny spellbook from her cruel slave master, and B) smuggle her home across the desert to the secret grove that houses her kind.
Can the PC's make it across the desert and survive long enough to learn their new powers before the Slave Owner's mercenaries catch up with them?
(Convert NPC levels to PC levels when the pixie gets home, magic classes from what she teaches, mundane classes from the adventure itself)
This can be used a prelude to a later campaign, as the heroes will turn with their powerful abilities at the end.